pkt_sched: set root qdisc before change() in attach_default_qdiscs()

After commit 95dc19299f74 ("pkt_sched: give visibility to mq slave
qdiscs") we call disc_list_add() while the device qdisc might be
the noop_qdisc one.

This shows up as duplicates in "tc qdisc show", as all inactive devices
point to noop_qdisc.

Fix this by setting dev->qdisc to the new qdisc before calling
ops->change() in attach_default_qdiscs()

Add a WARN_ON_ONCE() to catch any future similar problem.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 547b4a88ae2aa5fa9c850973cb6db9ad26e1035c..c31190e29b90212d8fe48fe3725692ae75b08af2 100644 (file)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -273,8 +273,11 @@ static struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle)
 
 void qdisc_list_add(struct Qdisc *q)
 {
+       struct Qdisc *root = qdisc_dev(q)->qdisc;
+
+       WARN_ON_ONCE(root == &noop_qdisc);
        if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS))
-               list_add_tail(&q->list, &qdisc_dev(q)->qdisc->list);
+               list_add_tail(&q->list, &root->list);
 }
 EXPORT_SYMBOL(qdisc_list_add);
 

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 6a91d7d48ade4818b09bc53901c90a009ddd508c..32bb942d2faad9a2922f3fcdec18770548f3d64c 100644 (file)
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -718,8 +718,8 @@ static void attach_default_qdiscs(struct net_device *dev)
        } else {
                qdisc = qdisc_create_dflt(txq, &mq_qdisc_ops, TC_H_ROOT);
                if (qdisc) {
-                       qdisc->ops->attach(qdisc);
                        dev->qdisc = qdisc;
+                       qdisc->ops->attach(qdisc);
                }
        }
 }